Treatment of hydrocarbon oils



Oct. 11, 1938. H. v. A'rwr-:LL

TREATMENT OF' HYDROCARBON OILS Filedpec. 31, 1957 INVENTOR H4/?0D K 4TH/[LL BY H' S ATTO RNEY eut coking diiiiculties.

invention these asphaltic materials which have Patented oct. 11, 193s UNITED STATES;

PATENT OFFICE to Process Management Company,

Inc., New

York, N. Y., a corporation of Delaware Application December 31, 1937 Serial No. 182,678

` 4 Claims.

This invention relates to the cracking of hydrocarbon oils for the production of lower boiiing products such as gasoline.

In accordance with the invention, hydrocarbon which it is desired to subject to cracking, is treated with a solvent capable of removing asphaltic materials that may be contained in the oil, the oil from which the asphaltic material is removed is subjected to a cracking operation and the asphaltic material is injected into` the oil undergoing cracking so as to thus subject the asphaltic material to cracking for conversion into lower boiling products.

The invention is especially directed to the processing of stocks containing residual constituents of crude petroleum, such as topped and reduced crudes. Such stocks contain greater or less proportions ci asphaltic constituents whichy are very readily converted into coke when the cil is subjected to cracking. By removing these potential coke-forming constituents from the oil, the oil is made susceptible to cracking under much more drastic conditions, characterized withv greatly increased rates of cracking perv pass with- In accordance with the been removed from the char-ging stock are injected into the stream of oil undergoing cracking so as to thus advantageously accomplish. the cracking of the asphaltic materials and effect conversion into additional gasoline. constituents.

In practicing the invention the charging stock is treated with a liquefied normally gaseous hydrocarbon, such as ethane, ethylene, propane,

propylene, butane, butylene, or mixtures thereof.,`

under conditions in which such hydrocarbon acts as an anti-solvent of the asphaltic constituents which are precipitated from the oil. The oil thus freed of the asphaltic, coke-forming constituents, may be subjected to cracking at a high rate of cracking per pass adapted to sustain a conversion into high anti-knock constituents and the precipitated asphaltic material is introduced into the cracked products so that the asphaltic material is raised to a cracking temperature and subjected to conversion. In this way the de-asphalted stock may be subjected to temperatures and longer times of reaction than are applied to the precipitated rmaterial which may be introduced into the crackzone at the latter portion thereof so that the precipitated material may thus be subjected to cracking for ashorter time than the deasphalted oil.

Although various solvents, or anti-solventsl of asphaltic material, may be employed in the practice of the invention, the hydrocarbons mentioned are well adapted for the purpose of the invention because of their excellent anti-solvent properties, at temperatures close to normal temperatures, with respect to asphaltic constituents contained Y in petroleum oils. Propane or va hydrocarbon gas consisting essentially of propane, is recommended because of its ready availability.

In order to more fully disclose the invention, reference will be had to the accompanying drawing, which is a flow diagram illustrating a particular embodiment of the invention.

In the drawing II! represents the oil stock tank 1.5

containing the oil which it is desired to treat, and H indicates a suitable source of liqueed propane maintained under appropriate pressure.. The oil is drawn by the pump I2 and passed through charging line I3 into a. mixer I 4 and the propane is drawn by pump I5 and passed through charging line I6 into the mixer I4. The charging line I3 is connected to a heating coil IT and the charging line I6 is connected to a heating coil` I8 so that the oil stock either or both, may be heated to maintain the desired temperature in the mixer I4 and in a settling tank I9 into which the mixer discharges.v The heating coils I1 and I8 may be heated in any appropriate manner, with products from the cracking operation, and the mixer I4 and settling tank. I9 are preferably insulated to retain heat and facilitate the accurate control of the temperature in the mixer and settling tank.

35 By reason of the contacting of the oil and the Solvent in the mixer and settling tank, asphaltic constituents are precipitated out of the oil solution and there is collected in the tank i9 a supernatent oil layer and a bottom layer of asphaltic material. The oil thusfreed of asphaltic ma terials flows into the cracking stock tank 20- andA the asphaltic material is drawn into the asphalt tank 2|. While the asphaltic material exists as potential solid material, it is removed as a liquid by reason of the fact that it is in solution with a certainv amount of the liquid propane and is with drawn to the asphalt tank. For purposes of simplicity, a single settling tank I9 is shown but it is to be understood that it is often desirable to employ a plurality of settling tanks to facilitate a better separation between the oil and the asphaltic material.

The de-asphalted cracking stock collecting in the tank 20 may, if desired, be freed of pro 55 and the propane, 25

as by heat exchange 30 pane by reduction in pressure and the flashed propane cycled to the propane tank H for reuse, or the cracking stock containing the propane in solution may be passed directly to the cracking zone. As illustrated, the pump 22 withdraws the de-asphalted cracking stock from the tank and directs it to a cracking coil 23, positioned in a furnace 24 adapted for supplying heat adequate for cracking. The coil 23 discharges into a -secondary cracking coil 25 positioned in a heating or heat-retaining chamber 26 and a pump 21 withdraws asphaltic material from the tank 2| and introduces this material through line 2B into the secondary cracking coil 25. The chamber 26 may be supplied with furnace gases from the furnace 24 or otherwise heated under conditions of relatively low heat density. In lieu of arranging the chamber 26 as an element separate from the furnace 24 the heating coil 25 may be disposed in the furnace 24 in a Zone of relatively low heat density therein. If desired, the asphaltic material being introduced into the coil 25 by the pump 21 may be preheated before being admitted to the cracking coil, as by means of a heating coil,29. In practicing the invention, the oil in the coil 23 is subjected to high cracking temperatures under conditions of high cracking per pass and the stream of cracked products flowing to the coil 25 is utilized in accomplishing the cracking of the asphaltic material introduced into the cracking coil 25.

The combined cracked products from the cracking coil 25 pass through transfer line 30 into a separator or vaporizer 3l wherein separation of vapors from residue takes place. The separated vapors are fractionated in fractionator 32 to separate as reflux condensate insuciently converted constituents from vapors which are condensed in condenser coil 33 and collected in receiver 34 as a desired product. Reux condensate collected in tower 32 is advantageously subjected to further cracking either by being cycled to the cracking coil 23 or by being directed to a separate cracking zone. In a preferred embodiment of the invention, the vapors in the tower 32 are subjected to a primary fractionation to separate out a relatively small quantity of primary reflux condensate which is collected at the bottom of the tower 32 and a much larger proportion of secondary reflux condensate collected on a trap-out tray 35. This operation is advantageous in removing from the vapors certain polymer products of cracking including certain tarry or asphaltic products of reaction and the heavy reflux condensate containing these materials is advantageously cycled by a pump 35 to the oil stock tank I0 so that it may be admixed with the charging stock for treatment with the solvent. The secondary reflux condensate may be cycled by a pump 37 to the cracking coil 23 or it may be passed to a separate cracking unit not shown.

The term asphaltic material as used herein refers to certain black, pitchy material existing in the oil as a potential solid or semi-solid. The

term is intended to apply to constituents having a melting point of about 80 F. or higher. Ordinarily in the treatment of crude petroleum residuum in accordance with the invention the asphalt precipitated out, upon removal of the solvent, will have a melting point of about 140 F. to 180 F. In accordance with the invention the solvent may be applied in a highly selective manner to separate out an asphalt, which upon removal of the solvent. may have a melting point of, for example, about 140 F. to 180 F. In practicing the invention under somewhat less selective conditions, while the oil may be substantially freed of asphaltic constituents, there may be certain proportions of oil constituents contained in the solvent-asphalt mixture which will lower the melting point.' The asphaltic material as removed from the oil by the action of the propane and collected in the tank 2|, will be in liquid form by reason of the presence of the liquid propane (ordinarily about 50% of propane by volume), and sometimes due also to the presence of a certain amount of oil constituents. The liquid solution of asphaltic material may be readily injected into the stream of cracked products to thereby accomplish the cracking of the asphaltic, coke-forming constituents in an advantageous way.

The selective action of propane as a precipitating solvent for asphaltic material contained in hydrocarbon oil is exhibited at temperatures of about 70 F. to about 150 F. An advantageous temperature is 100 F. to 140 F. with volumes of liquid propane of about three to ten to one volume of oil. Under these conditions the action of the solvent is highly selective in precipitating asphalt with a minimum removal of oil. As the temperature is raised increased proportions of oil will be contained in the solvent-asphalt mixture.

With ratios of propane to oil of as low as three to four to one at a temperature of 120 F. substantially all of the asphaltic material may be precipitated out from the oil. The de-asphalting is carried on under pressures appropriate for maintaining the solvent in liquid form under the temperatures used and may well be carried on under pressures of about 250 to 400 pounds.

The solvent treatment may be employed to remove from the oil, in addition to asphaltic constituents, certain resinous constituents. By removing the resins, as well as the asphaltic material, the treated oil is further improved as a cracking stock with respect to coke-forming proclivities. Ihe resinous fraction may be removed together with the asphaltic material, or if desired, the oil may rst be treated with the solvent to remove asphalt and then further treated with the solvent to remove the resins. In the twostage operation it is preferable to use a slightly higher temperature for the resin-removing operation, thus for example with ratios of propane to oil of 4-6z1 and with temperatures of about 13G-135 F. for the de-asphalting stage; temperatures of about 150-1'75 F. may be used in the de-resinifying operation. Both the asphaltic and resinous fractions may be conducted to the reaction coil 25 so that these materials may be converted into lower boiling products.

The de-asphalted stock, either with or without the removal of solvent, is passed to the cracking coil 23 and subjected t'o relatively drastic cracking conditions therein to effect conversion into gasoline constituents of superior anti-knock quality. By way of example, it may be stated that the deasphalted stock may be subjected to cracking temperatures of 900 F. to 1000 F. with a time of reaction in the coil 23 adequate to effect a conversion per pass (as measured by conversion into 400 F. endpoint gasoline) of 20% to 30%. The asphaltic material, and the resinous material and certain heavy oil constituents that may be included with it, preferably after having been preheated to temperatures, such as 600 F. to 800 F., is injected into the stream of cracked products discharging from the cracking coil 23 to thus raise the asphaltic material to a high Vcracking temperature, such as about 900 F., and

effect the cracking of the asphaltic constituents. In this way the asphaltic constituents may be subjected to a high rate of conversion tending to the formation of gasoline constituents of superior anti-knock quality. The cracking operation in the coils 23 and 25 is carried on under superatmospheric pressure, such for example as 400 to 800 pounds, and the pressure on the cracked products is preferably reduced in the evaporator 3| to facilitate the distillation of cracked products. Appropriate reuxing is carried on in the tower 32 to form a relatively small quantity of high boiling reflux condensate which may contain certain asphaltic or tarry products of reaction and this heavy reflux condensate is advantageously cycled to the oil stock tank I0. The lighter reflux condensate collected on the trap-out tray 35 is subjected to further cracking as by being cycled to the cracking coil 23 and the desired gasoline product is collected in the receiver 34.

The Xed gases from the receiver 34 or the fixed gases obtained in rectifying the product collected in 34, may advantageously be cycled to the solvent storage tank Il to be mixed with the solvent therein. In the operation in which the deasphalted cracking stock passing to the tank 20 is not freed of its xed gas content, the fixed gases contained in the oil passing to the cracking coils 23 and 25 will undergo reversion reactions therein so as to thus increase the conversion into gasoline. It is thus advantageous to cycle the fixed gases, particularly the Css and C-is, removed from the final distillate of the process, to the solvent tank Il so as to obtain not only the solvent value of the gases in the asphalt removal step but also to increase the reversion reactions occurring in the cracking zone.

While I have described a particular embodiment of my invention for purposes of illustration, it should be understood that various modifications and adaptations thereof which will be obvious to one skilled in the art, may be made within the spirit of the invention as set forth in the appended claims.

I claim:

1. In the conversion of higher boilng hydrocarbon oil into lower boiling hydrocarbons, the process that comprises treating hydrocarbon oil with a liqueed normally gaseous hydrocarbon to thereby precipitate asphaltic material, passing the treated oil to a cracking zone wherein the oil is heated in a owing stream to a cracking temperature and subjected to cracking, and introducing the asphaltic precipitate into said flowing stream of oil at a point therein at which the stream is at a cracking temperature to thereby subject the asphaltic material to cracking.

2. In thev conversion of higher boiling hydrocarbon oil into lowerboilng hydrocarbons, the process that comprises treating hydrocarbon oil with a solvent of the oil under conditions in 'which the solvent is an anti-solvent of asphaltic material to thereby precipitate asphaltic material contained in the oil, passing the treated oil to a cracking Zone wherein the oil is heated in a flowing stream to a cracking temperature and subjected to cracking, and introducing the asphaltic precipitate into said flowing stream of oil at a point therein at which the stream is at a cracking temperature to thereby subject the asphaltic material to cracking.

3. In the conversion of higher boilng hydro# carbon oil into lower boiling hydrocarbons, the process that comprises treating a hydrocarbon charging stock with a liquefied normally gaseous hydrocarbon to thereby precipitate asphaltic material, passing the treated oil to a cracking Zone wherein the oil is heated in a flowing stream to a cracking temperature and subjected to cracking, introducing the asphaltic preciptate into said flowing stream of oil at a point therein at which the stream is at a cracking temperature to thereby subject the asphaltic material to cracking, separating the resultant cracked products into vapors and residue, fractionating the separated vapors to form a heavy reilux condensate, an intermediate condensate and a final distillate product, and combining the heavy reflux condensate with the charging stock for treatment with said liquefied normally gaseous hydrocarbon.

4. In the conversion of higher boilng hydrocarbon oil into lower boilng hydrocarbons, the process that comprises treating a hydrocarbon charging stock with a liquefied normally gaseous hydrocarbon to thereby precipitate asphaltic material, passing the treated oil to a cracking zone wherein the oil is heated in a flowing stream to a cracking temperature and subjected to cracking, introducing the asphaltic precipitate into said flowing stream of oil at a point therein at which the stream is at a cracking temperature to thereby subject the asphaltic material to cracking, separating the resultant cracked products into vapors and residue, fractionating the separated vapors to form a heavy reflux condensate, an intermediate condensate and a nal distillate product, subjecting the intermediate condensate to further cracking and combining the heavy reflux condensate with the charging stock for treatment with said liquefied normally gaseous hydrocarbon.

HAROLD V. ATWELL. 

